===== Graphic VRAM =====


 The structure of G-VRAM differs depending on the actual screen size
and the number of colors. A total of 512 KB of VRAM is divided and
allocated.

The pixel representation is a linear type and in any mode one pixel
is represented by one word. In the 16/256 color display mode only the
lower 4/8 bits are effective.

	X = X coordinate in normal mode
	Y = Y 〃
	P = Plane number
	ADR = 65536 color display mode address (X,Y)
	BIT = 〃 bit position

**Real screen 512×512 pixels、65536 color display**
| Valid bits  | Full 16 bits             |
| 1 Row       | 1024 bytes(512 words)  |
| Page 0      | $c00000～$c7ffff        |

**Real screen 512×512 pixels、256 color display:**
|Valid bits|Lower 8 bits|
|1 Row|1024 bytes(512 words)|
|Page 0|$c00000～$c7ffff|
|Page 1|$c80000～$cfffff|

	ADR = $c00000＋Y×1024＋X×2
	BIT = P×8 ～ P×8＋7 for 8 bits

**Real screen 512×512 pixels、16 colors**
|Valid bits|Lower 4 bits|
|1 Row|1024 bytes(512 words)|
|Page 0|$c00000～$c7ffff|
|Page 1|$c80000～$cfffff|
|Page 2|$d00000～$d7ffff|
|Page 3|$d80000～$dfffff|

	ADR = $c00000＋Y×1024＋X×2
	BIT = P×4 ～ P×4＋3 for 4 bits

**Real screen 1024×1024 pixels、16 colors:**
|Valid bits|Lower 4 bits|
|1 Row|2048 bytes(1024 words)|
|Page 0|$c00000～$dfffff|

	ADR = $c00000＋(Y＆511)×1024＋(X＆511)×2
	BIT = (Y≧512)×8＋(X≧512)×4 ～
	      (Y≧512)×8＋(X≧512)×4＋3 for 4 bits		  

===== Text VRAM =====

 T-VRAM has a real screen size of 1024x1024 pixels fixed to 16
color display and 4 planes for a total of 512KB. Pixel representation
is planar type, 1 word is 16 horizontal pixels. Each plane represents
1 bit of the 4-bit palette code.

|1 Row|128 bytes(64 words)|
|Page 0|$e00000～$e1ffff|
|Page 1|$e20000～$e3ffff|
|Page 2|$e40000～$e5ffff|
|Page 3|$e60000～$e7ffff|